Hi there

The on-screen keyboard (pic below) should appear on the screen upon pressing the 'select' or 'OK' button upon going into the password box.

Step 1:

When you get to this Screen:

Step 2:

Press this button:

Step 3:

This screen will appear - Type in your Wifi password.  To change to upper and lower case, use the Up arrow button on the onscreen keyboard

Cheers